Wave length modulation



y March 20, 1945. w.v VAN B. ROBERTS 2,372,012.`

f wAvE LENGTH MoDuLATIoN R-Y Filed oct. 12, 1942 ATTORNEY l Mandar/0N Patented Mar.. 20, 194.5

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WAVE LENGTH MonULA'r'IoNa waiter. van n, nahme, .Princeton N. .1., assigner' to: Radio Corpora-.tion of America, a corporation of Delaware. l

Application october 12, 1942-,.-sericr-"No.reime 1,-

v Claims.

This application concerns a. new and improved timing .or wave length modulation system. `By the expression timing or wave lengthmodulation applicant vmeans a. system wherein the instantaneous frequency of Wave energy is con- 5 trolled in' accordance with signals or controlpo- 'tentials This control ormodulatlon may he. as to phase or frequency or modified forms of either crboth depending on the treatment of the .poten- (ci. warms). ,Y

reactance circuit "including L' so 'that 'the said tubes with 'theircoupllngsf produce susceptance across the tank circuit C# Tubes-i0 and t0 are coupled bya reactive coupling Cof Isign"opposite to `that in :the coupling between Vtubes tlljand Uso that 'they provide therein and across the tank circuit Tsusceptaznc o-f a sign opposite 4to thejsusceptance provided by 'tubes 80 and 40 across the tank circuit 'Tr The tials'used to. control the instantaneousfirennency '10 'gainpf the ampliers '30and 4U. 'and ill'and 55B of the wave energy.

In' describing .my invention, lreference will bemade to thedrawing, wherein Figuresxl and 2 each shows a modification of a wave length .mod-

ulation system .arranged in accordance. withmy invention.

In Figure 1 T is a tank circuit, a polnton which is.coup1ed tothe grids 9,29, and .49 of-.tubes 11:30 and .50. The tank circuit isgrounled at one end and it.. is. also coupled by radio-frequencycou# 2@ Ap'ling condensers. to the anodes .2 L'. 4l andl. of

tubes '4B and 6B. Tube lll has itsanodeil' coupled by a circuit 'including resstanceRanda coupling condenserto .the grid vI9 of.tube 2d.

"Tubefm hasits anode 3l..coupled..by av circuit 25 jinclu'cling'tulxes 4wand 2S; While plate modulaincludingiinductancelanda coupling condenser 'tion has-peenmentioned'. this is for the 'puriJQSe tothe grid of..tube $0. Tube llihasits anode BE coupled by a circuit including a capacitive yreactance .Canda c'ouplingcondenser--to the grid 59st tubelll. f

The direct current blascircuit .for tubes. in, rat and 50 include a grid leak and condenser arrangement-l5. ,.Thedirect-current bias circuits for the grids of tubes 20, d and E@ include resistors Il. 31 and 5l.' may becpnnected to ground directly'or by resistances where additional bias is desired.

The cathodes of the several tubes' 35 The anodescf tubes 40 and 60 are also connected through radiofrequency chokes-RFC to the secondary winding of a. transformer B3, the 4U conductance through the tubes I0 and 20 and 45 across the tank circuit so that considering' these tubes as amplifiers, oscillations are produced therein and in the tank circuit. of a frequency determined primarilyby the tuning Voi the tank circuit T. It will be understood that for high- 50 frequency operation the element R will be a network of a type -Well known in the art of broad .band amplifiers for producing the eliect of a'pure resistanceover a band of frequencies.

Tubes and 40 are coupled by an inductive 56 'are made'equalin 4the absence of modulation lso that they areequaland ciiseueach other normally so that "the systemcperates tofproduce oscilla- -tions of'a frequency equal to the Anatural 'fretifafllyitorthe'anodes-'lli'y and Gl'of tubes 4t and 60,. f

thatis, -the Itubesin-tl'ietwo susceptance producing networks, the -net fsuscep'tance Iwill, become positiveor negative 'according to ythepolarity of the modulation voltage and oscillations Will `be modulated in frequency. Therewill be'no ampli-,- -tudemodulation because no modulation is Iapplied tothe lnegative conductance lproducing 'system oi'speci'c illustration as other types of modula- '-ln themvdication lof-Figure 2,:three tubes 2H", lili, 4and tu have their ancdes 2&2 'l`i",vand '6i' coupled, 'as -shown,'to the tank circuit T2' The tube '-20' has its control-grid t9' coupled to, a point -on-the tank v,circuit Tby 4a concentric line Land 'a gridbiasing arrangement l5: L'is f aLlength of the order of M2.y The control grid 39"of tube is connected through l 5 to the tank circuit bya line'LZ, the length of which is of the order of 'Ni/4. The control grid 59' of tube 60 is coupled through I5 to the tank circuit T by a line NSX/4 in length, where N is a whole odd number.

The modication of Figure 2 operates in'prnciple the same as the modification in Figure 1' except that a single tube is included in the negative conductance lnetwork and made to supply negative conductance across the tank T by virtue of the phase reversing action of the half wave length line L. The susceptance supplying netlworks include single' tubes 40' and 60 having their control .electrodes coupled to the tank circuit T by concentric lines L2 and L3, of which Ll is of a 1A wave length, whileLZ is of a length' increases andthe other decreases so that the netI susceptance across the tank circuit becomes positive or negative according to the polarity of the modulation potentials applied to the anodes. Here, as in Figure l, there will be no amplitude modulation because no modulation potential is applied to the negative conductance system, includingtu'oe 20' and line L.

What is claimed is:

l. A wave length modulation system comprising a tank circuit, an amplifier coupled'to said tank circuit and operated to produce thereacross a negative conductance, a second ampliiier coupled to said tank circuit and operated to produce thereacross positive susceptance, a third amplifier coupled to said tank circuit and operated to produce thereacross negative susceptance substantially, equal to said positive susceptance and connections for dierentially controlling the ampliilcation of said second and third ampliiiers in accordance with control potentials.

2. A wave length modulation .system comprising a tank circuit, a tube amplifier coupled across said tank circuit and operated to produce thereacross a negative conductance, a second tube amplifier coupled across said tank circuit and- 4operated. to produce thereacross positive susceptance, a third tube amplifier coupled across said tank circuit and operated to produce thereacross negative susceptance substantially equal to said positive susceptance and connections for difierentially controlling the amplification of said second and third amplifiers in accordance with control potentials.

3. A wave length modulation system comprising a tank circuit, an amplifier coupled across said tank circuit by a line the length of which is about M2 to produce across said tank circuit a negative conductance, a seco-nd amplifier Vco'upled across said tank circuit by a line the length of opposite sign 4. In a wave length modulation system, a tank circuit, a rst pair of electrondischarge devices, each having input and output electrodes, a coupling between the input electrodes of one of said discharge devices and said tank circuit, a coupling between the output electrodes of the other of said discharge devices and the tank circuit, a .resistivev coupling between the output electrodes of the iirst of said discharge devices and the input electrodes of the second of said pair of discharge devices, a second pair of electron discharge devices each having input electrodes and output electrodes, an inductive coupling between the 'output electrodes of one of said devices of said second pair and the input electrodes of the other device of`said second pair, a coupling between the input electrode of said one of said deof' which is less than M2 to' produce across said tank a positive susceptance, a third ampliiier coupled across said tank circuit by a line the length of which is more than M2 to produce a negative susceptance and connections for differentially controlling the amplification of said second and third ampliners in accordance with control` potentials.

-vices of said second pair and the tank circuit, a coupling between the output electrodes of the other of said devices of said second pair and the tank circuit, a third pair of electron discharge devices each having input and output electrodes, a capacitive coupling between the output electrodes of one of said devices of the third pair andthe input electrodes of the other of the devices of the third pair, a coupling between the input electrodes of said one of said devices of the third pair and the tank circuit; a coupling between the output electrodes of the other of said devices of the third pair and the tank circuit and means for diierentially modulating the amplification of at least one device vof said second and third named pairs of devices differentially in` accordance with control potentials y 5. In a wave length modulation system, a tank circuit, an amplifier having an input and an output with its input coupled to its output by said tank circuit and operated to produce through ksaid amplifier and in the ytank circuit negative conductance, a second amplifier having an input and an output with its input coupled to its out- `put by said tank circuit and operated to produce through said second ampliiier and in said tank circuit positive susceptance, a third amplifier having an input and an output with its input coupled to its output by said tank circuit and operated to produce through said third amplifier and in said tank circuit negative susceptance substantially equal to said positive susceptance, and connections for dierentially controlling the 1 ampliiicatiori of said second and said third ampliiiers in accordance with control potentials.

WALTER VAN B. ROBERTS. 

